The lithium ion battery is a relatively new and environmentally friendly electro-chemical energy source. When compared with the traditional nickel cadmium battery and nickel hydrogen battery, a lithium ion battery has the advantages of having higher voltage, longer life, and large energy density. It is also lightweight, has no memory effects, and is less harmful to the environment. Because of these superior characteristics, the lithium ion battery has developed rapidly and is now widely used in portable equipment.
The negative electrode of traditional lithium ion batteries uses graphitized carbon materials such as natural graphite, artificial graphite, and non-graphitized carbon materials such as non-graphitized charcoal, charcoal obtained from oxidizing macromolecule materials of poly-hydrocarbon at high temperatures, pyrolytic carbon, coke, calcined organic macromolecule, and active carbon. However, these carbon materials form a SEI (surface electrolyte interface) on the surface layer of the carbon material during the initial charging process. The formation of the SEI and other reactions in the electrolyte reduces the initial charge-discharge electrical efficiency and affect the performance of a battery's capacity.
Adding a quantity of lithium alloy to the material for the negative electrode can effectively solve the problem of decreasing battery capacity resulting from the reduction of initial charge-discharge electrical efficiency. However, this volume of the added lithium alloy will expand with the continuous charge-discharge process of a battery. This will cause the loosening of materials in the electrode, and can even cause the material of the electrode to detach. This process also increases the internal resistance and affects the cycling properties of the battery.
Due to the limitations of the prior art, it is therefore desirable to have novel materials and novel methods of fabricating materials for negative electrodes such that, when these materials are used in negative electrodes of batteries, produces batteries with excellent initial charge-discharge efficiency, large battery capacity, and long cycling life.